Gas Permeability
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2022 ◽  
Yuan-Jian LIN ◽  
Jiang-Feng LIU ◽  
Tao CHEN ◽  
Bing-Xiang HUANG ◽  
Kundwa Marie Judith ◽  

Abstract In this paper, a THMC (Thermal-Hydrological-Mechanical-Chemical) multi-field coupling triaxial cell was used to systematically study the evolution of gas permeability and the deformation characteristics of sandstone. The effects of confining pressure, axial pressure, and air pressure on gas permeability characteristics were fully considered in the test. The gas permeability of sandstone decreases with increasing confining pressure. When the confining pressure is low, the variation of gas permeability is greater than the variation of gas permeability at high confining pressure. The gas injection pressure has a significant effect on the gas permeability evolution of sandstone. As the gas injection pressure increases, the gas permeability of sandstone tends to decrease. At the same confining pressure, the gas permeability of the sample during the unloading path is less than the gas permeability of the sample in the loading path. When axial pressure is applied, it has a significant influence on the permeability evolution of sandstone. When the axial pressure is less than 30 MPa, the gas permeability of the sandstone increases as the axial pressure increases. At axial pressures greater than 30 MPa, the permeability decreases as the axial pressure increases. Finally, the micro-pore/fracture structure of the sample after the gas permeability test was observed using 3D X-ray CT imaging.

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 70
Zhaoying Chen ◽  
Guofu Li ◽  
Yi Wang ◽  
Zemin Li ◽  
Mingbo Chi ◽  

Underground coal mining of CH4 gas-rich tectonic coal seams often induces methane outburst disasters. Investigating gas permeability evolution in pores of the tectonic coal is vital to understanding the mechanism of gas outburst disasters. In this study, the triaxial loading–unloading stresses induced gas permeability evolutions in the briquette tectonic coal samples, which were studied by employing the triaxial-loading–gas-seepage test system. Specifically, effects of loading paths and initial gas pressures on the gas permeability of coal samples were analyzed. The results showed the following: (1) The gas permeability evolution of coal samples was correlated with the volumetric strain change during triaxial compression scenarios. In the initial compaction and elastic deformation stages, pores and cracks in the coal were compacted, resulting in a reduction in gas permeability in the coal body. However, after the yield stage, the gas permeability could be enhanced due to sample failure. (2) The gas permeability of the tectonic coal decreased as a negative exponential function with the increase in initial gas pressure, in which the permeability was decreased by 67.32% as the initial gas pressure increased from 0.3 MPa to 1.5 MPa. (3) Coal samples underwent a period of strain development before they began to fail during confining pressure releasing. After the stress releasing-induced yield stage, the coal sample was deformed and cracked, resulting in a quickly increase in gas permeability. With a further releasing process, failure of the sample occurred, and thus induced rapidly increasing gas permeability. These obtained results could provide foundations for gas outburst prevention in mining gas-rich tectonic coal seams.

2021 ◽  
Vol 9 ◽  
Ziya Zhang ◽  
Kun Zhang ◽  
Yan Song ◽  
Zhenxue Jiang ◽  
Shu Jiang ◽  

Similar to North America, China has abundant shale resources. Significant progress has been made in the exploration and exploitation of shale gas in China since 2009. As the geological theory of unconventional oil and gas was proposed, scientists have started researching conditions for shale gas preservation. The shale roof and floor sealing and the shale self-sealing are the critical objects of such research, which, however, are still in the initial stage. This article studies the formation mechanism of shale roof and floor sealing and shale self-sealing by taking marine shales from Member I of the upper Ordovician Wufeng Formation–lower Longmaxi Formation in the upper Yangtze region as the research object. Analyses were performed on the TOC content, mineral composition, and porosity, as well as the FIB-SEM, FIB-HIM, and gas permeability experiments on the core samples collected from the marine shales mentioned above. The conclusions are as follows: for the sealings of shale roof and floor, the regional cap rocks, roof, and floor provide sealing for shales due to physical property differences. For the self-sealing of shales, the second and third sub-members of Member I of the Wufeng Formation–Longmaxi Formation mainly develop clay mineral pores which are dominated by macropores with poor connectivity, while the first sub-member of Member I of the Wufeng Formation–Longmaxi Formation mainly develops organic-matter pores, which are dominated by micropores and mesopores with good connectivity. Owing to the connectivity difference, the second and third sub-members provide sealing for the first sub-member, while the methane adsorption effect of shales can inhibit large-scale shale gas migration as it decreases the gas permeability; thus, the organic-rich shales from the first sub-member of Member I of the Wufeng Formation–Longmaxi Formation provides sealing for itself.

В.О. Попов ◽  
В.Н. Комов ◽  
Е.М. Попенко ◽  
А.В. Сергиенко

Данная статья посвящена исследованию влияния пористости прессованных таблеток из сверхтонкого порошка алюминия (СТП Al). Определен механизм горения, протекающий в две стадии: первая, медленная, включающая в себя как «кольцевое» горение боковой поверхности, так и параллельное горение концентрическими слоями, вторая стадия объемная, сопровождающаяся резким самопроизвольным увеличением температуры горения и интенсивности свечения. Показано, что увеличение плотности упаковки СТП Al позволяет замедлить процесс окисления алюминия более чем в два раза. Это обусловлено снижением газопроницаемости таблетки и затруднением доступа воздуха вглубь образца. Повышение пористости материала позволяет регулировать процесс нитридообразования за счёт увеличения содержания азота в продуктах при фильтрационном механизме горения, что открывает возможности получения тугоплавких материалов. This article is devoted to the study of the effect of porosity of compressed tablets from ultrafine aluminum powder (STP Al). The combustion mechanism was determined, which proceeds in two stages: the first, slow, which includes both "ring" combustion of the side surface and parallel combustion with concentric layers, the second stage is volumetric, accompanied by a sharp spontaneous increase in the combustion temperature and glow intensity. It has been shown that an increase in the packing density of HFC Al makes it possible to slow down the process of aluminum oxidation by more than two times. This is due to a decrease in the gas permeability of the tablet and the difficulty of air access deep into the sample. An increase in the porosity of the material makes it possible to regulate the process of nitride formation by increasing the nitrogen content in the products during the filtration mechanism of combustion, which opens up the possibility of obtaining refractory materials.

Simon J. A. Houben ◽  
Joey Kloos ◽  
Zandrie Borneman ◽  
Albert P. H. J. Schenning

Foods ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3105
Hui Chen ◽  
Mahafooj Alee ◽  
Ying Chen ◽  
Yinglin Zhou ◽  
Mao Yang ◽  

Edible starch-based film was developed for packaging seasoning applied in instant noodles. The edible film can quickly dissolve into hot water so that the seasoning bag can mix in the soup of instant noodles during preparation. To meet the specific requirements of the packaging, such as reasonable high tensile properties, ductility under arid conditions, and low gas permeability, hydroxypropyl cornstarch with various edible additives from food-grade ingredients were applied to enhance the functionality of starch film. In this work, xylose was used as a plasticizer, cellulose crystals were used as a reinforcing agent, and laver was used to decrease gas permeability. The microstructures, interface, and compatibility of various components and film performance were investigated using an optical microscope under polarized light, scanning electron microscope, gas permeability, and tensile testing. The relationship was established between processing methodologies, microstructures, and performances. The results showed that the developed starch-based film have a modulus of 960 MPa, tensile strength of 36 Mpa with 14% elongation, and water vapor permeability less than 5.8 g/m2.h under 20% RH condition at room temperature (25 °C), which meets the general requirements of the flavor bag packaging used in instant noodles.

2022 ◽  
Vol 29 (1) ◽  
pp. 12
Qiangxing Zhang ◽  
Jianfeng Liu ◽  
Zhide Wu ◽  
Lu Wang ◽  
Chaofu Deng ◽  

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